1. Field of the Invention
The present invention relates to an X-ray apparatus, and a rotary anode X-ray tube applied to an X-ray apparatus.
2. Description of the Related Art
An X-ray apparatus using a rotary anode X-ray tube is composed of a rotary anode X-ray tube main body which contains a rotatably supported anode target in a vacuum enclosure, a stator coil which supplies a driving magnetic field from the outside of the X-ray tube main body to a rotor connected to the anode target, and a housing which contains the X-ray tube main body and stator coil.
The space between the housing and rotary anode X-ray tube main body is filled with a cooling medium to radiate the heat generated from the anode target, for example, insulating oil and non-oil/fat cooling liquid including water as a main component. Namely, the heat from the anode target is radiated to the cooling medium, and the cooling medium is cooled by convection, and the heat is exhausted. As a result, a heating element such as an anode target is cooled. In this time, the heat generated from the stator coil is also exhausted, and the stator coil is cooled as a result. Cooling by using this kind of enclosed cooling medium is often adopted for a relatively small X-ray tube having sufficient heat capacity. (Refer to Jpn. UM Appln. KOKAI Publication No. 58-164171, for example.)
An example of using antifreeze solution having a high thermal conductivity among non-oil/fat cooling liquid as a cooling medium for the stator coil and rotary anode X-ray tube has been proposed. (Refer to PCT National Publication No. 2001-502473, for example.)
However, when oil/fat-based cooling liquid is used as a cooling medium, impregnant varnish used widely as an insulation coating material of a stator coil is eluted to the cooling medium, and the insulation of the stator and insulating oil themselves is lowered, and the life of an X-ray apparatus is reduced.
Further, when using non-oil/fat cooling liquid is used as a cooling medium, another problem arises. As the electrical conductivity of non-oil/fat cooling liquid is higher than that of oil/fat-based cooling liquid, the insulation of the stator coil must be ensured.